Heretofore, for example, JP8(1996)-338222A and JP53(1978)-118640A disclose an electromagnetic PCV valve arranged to control an open/closed position of a valve element according to an operating state of an engine. In JP8(1996)-338222A, a columnar valve element having a conical leading end is placed to be changeable in a position in an axial direction to change a flow sectional area of a blow-by gas passage according to the position of the valve element with respect to the valve seat. A rear end of this valve element is connected to a shaft whose end is attached with a columnar plunger made of ferromagnetism metal. Around this plunger, a coil is arranged at a distance therefrom. When this coil is energized under control of a controller according to an operating state of an engine, the plunger is moved by an electromagnetic force of the coil to move the valve element in the axial direction, thereby changing the blow-by gas flow sectional area between the valve element and the valve seat. JP53(1978)-118640A also discloses a PCV valve similar to the electromagnetic PCV valve of JP8(1996)-338222A.
Furthermore, JP61(1986)-122313U and JP60(1985)-98709U disclose a PCV valve provided with a valve case internally including a valve chamber and an electric heater serving as a special heating means disposed on the outer periphery of the valve case. This electric heater can heat the valve element and the valve seat placed in the valve chamber.